Under operator control, a railroad locomotive supplies motive power (traction) to move a train and applies brakes on the locomotive and/or on train railcars to slow or stop the train. The motive power is supplied by electric traction motors responsive to an AC or DC signal generated by the locomotive engine. The braking system comprises rail car air brakes and locomotive independent air brakes both responsive to air pressure in a brake pipe that runs a length of the train. The braking system further comprises dynamic brakes that generate slowing forces by operating the electric motors as generators, with the forces required to turn the motor/generator produced by the inertia of the train.
A train configured for distributed power (DP) operation comprises a lead locomotive at a head-end of the train and one or more of remote locomotives at an end-of-train position and/or disposed between the head-end and the end of the train. The system further comprises a distributed power train control and communications system with a communications channel (e.g., a radio frequency (RF) or a wire-based communications channel) linking the lead and remote locomotives.
The DP system generates traction and brake commands at each remote locomotive responsive to operator-initiated (i.e., the operator in the lead locomotive) control of a lead locomotive traction controller (or throttle handle) or a lead locomotive braking controller (responsive to operation of the air brake handle, dynamic brake handle, or independent brake handle). These traction or braking commands are transmitted to the remote locomotives over the DP communications channel. Each receiving remote locomotive responds to the traction or brake commands to apply or reduce tractive effort or to apply or release the brakes. Each remote locomotive further advises the lead locomotive that the command was received and executed. For example, when operating in one DP system mode (referred to as synchronous mode), the lead locomotive operator operates the lead-locomotive throttle controller to apply tractive effort of the lead locomotive according to a selected throttle notch number. The DP system issues commands to each remote locomotive to apply the same tractive effort (e.g., the same notch number). Each remote locomotive replies acknowledging execution of the command.
The lead locomotive also issues status request messages and the remote locomotives respond, for example with operational data. The lead and remote locomotives can also issue alarm messages to the other locomotives of the train.
In general, traction and braking messages sent over the distributed power communications system result in the application of more uniform tractive and braking forces to the railcars, as each locomotive can effect a brake application or release at the speed of communications channel signal rather than the slower speed of the pneumatic brake pipe pressure change that must propagate along the entire train. Distributed power train operation may therefore be preferable for long train consists to improve train handling, especially braking applications, and performance. Trains operating over mountainous terrain realize tangible benefits from DP operation.
Communications losses are particularly troublesome in a train configured for DP operation. To thoroughly analyze the communications loss it is necessary to know the location of the train when the loss occurred. For example, the communications loss may be due to a physical obstruction in the DP system communications path or due to an interfering signal in the area where the loss occurred. Although such losses are verbally reported by the crew to appropriate personnel (e.g., in a remote dispatch center), the lack of accurate location information when the loss occurred hampers determining the root cause of the problem.
The analysis of other train and locomotive problems can also be aided by location information. With information of the train/locomotive location when the problem or event occurred, a correlation between the condition of the railroad infrastructure (e.g., track, signals) and the observed problem can be determined.